This invention relates to machine tools and is particularly concerned with machines for machining or shaping gears, such as spiral and hypoid pinions and crown gears, or slots. In particular, the invention may be applied to machines for rough-cutting and/or finishing such gears or slots with cutting tools and/or grinding wheels.
The invention is particularly applicable to a machine for machining a workpiece to provide a curved-tooth bevel gear. Generally, the invention is concerned with a machine comprising a workpiece support angularly displaceable about a first axis, a tool support angularly displaceable about a second axis and which is constructed to support an annular tool for rotation about a third axis, angled to the first axis, so that a supported tool can not only rotate about its own axis but can also be displaced on an arcuate path about the second axis, and control means for controlling the relative movements about the first axis and at least one of the second and third axes, while the rotation about the third axis is independent of the motions about the first and second axes.
All known spiral bevel gear manufacturing equipment in current use for cutting or grinding slots or spiral gear teeth, e.g. the Gleason machine, incorporate extensive gear trains to effect control between the first and second axes.
U.S. Pat. 3,879,898 relates to a machine of the kind as described above, wherein the control means is in the form of an electrical master-slave servo system for controlling the relative movements.
In one embodiment according to that U.S. Patent Application, the workpiece support is slaved to the tool support and oscillates during machining.
In another embodiment, described as a modification of an existing machine tool, the workpiece support rotates during machining, being slaved to a continuously rotating part of the master so that its rotation is controlled to be dependent upon the rotation of that part, which in that case is a lobed cam forming part of the existing machine. This cam is driven, by an extensive gear train, to rotate between two guides mounted on the tool support. The rotation of the cam thereby oscillates the tool support.